Aspects of the influence of magnesium ions on the formation of calcium oxalate.

The influence of magnesium ions on the solubility and formation of calcium oxalate was studied. Both calcium oxalate mineral constituents of urinary calculi (whewellite and weddellite) were prepared in the presence of Mg2+ions. For preparation, a gel growth technique and precipitation in aqueous solutions were used. The metastable weddellite formed only when Mg2+ concentration, reaction, temperature and precipitation velocity (see text) were combined in the proper way. It is concluded that mg2+ions may induce an increase of solubility of calcium oxalate but in contrast also broaden the Ostwald Miers range, thus favouring the formation of larger crystals.